The present invention relates generally to a substrate connector, and more particularly to substrate connector with improved contact force characteristics.
Conventional flat connectors that use a large number of terminals are used to connect a semiconductor device to a circuit board or to connect two substrates with each other. An example is shown in Japanese Patent Application Laid-Open (Kokai) No. 08-222335). FIG. 13 is a cross-sectional view of a conventional connector.
In FIG. 13, 801 represents a connector housing that has an upper housing 803 with an opening 804 and a lower housing 805 with a bore 806. 810 is a connector terminal provided with a base 811 mounted in the bore 806, a contact arm 813 that is bent from the base 811 and extending upward, and a contact part 812 protruding downward from the lower end of the base portion 811. When the terminal 810 is inserted into the bore 806 from above, the lower end of a wing 815 protrudes sideways from the terminal 810 and abuts against the bottom surface 808 of a groove 807 in the side of the bore 806 which limits the downward movement of the terminal 810. A portion of the upper surface of the bore 806 is covered by the upper housing 803 in order to restrict upward movement of the terminal 810. Hence, the terminal 810 is prevented from coming loose from the bore 806 and is firmly held by the housing 801.
Further, the terminal contact part 812 protrudes downwardly more than the bottom surface of the lower housing 805 and comes into contact with a conductive pad 821 formed on the upper surface of the substrate 820. A solder ball 831 formed on the lower surface of the semiconductor device 830 is kept in contact with a tip end part 814 of the contact piece 813 of the terminal 810. This provides electrical continuity between the conductive pad 821 and the solder ball 831 via the terminal 810.
In this type of connector the up and down movement of the terminal 810 is restricted, and when the spacing between the bottom surface of the lower housing 805 and the upper surface of the substrate 820 changes, this spacing change can only be absorbed within a range of plastic deformation permitted for the contact part 812 and the tip end part 814 of the terminal 801. When a change occurs that exceeds the range of elastic deformation, the terminal 810 is not permitted to smoothly move up and down and no longer keeps contact with the conductive pad 821. The semiconductor device 830 or the substrate 820 may include more and more terminals and become larger in its size and therefore, a variation in the vertical position of the solder ball 831 (or conductive pad 821) may increase, thereby preventing secure contact. In addition, vertical forces exerted by the semiconductor device 830 or the substrate 820 cannot be absorbed by the terminal 810, and the terminal 810 may buckle eventually, resulting in its breakage. It then becomes unable to stabilize the force, whereby the contact point 812 and the tip end part 814 contact the conductive pad 821 and the solder ball 831, respectively, which fails to keep secure connection. Additionally, because the upper and lower housings 803,805 are joined together to form the housing 801, the assembly process becomes complicated, resulting in an increase in cost. Furthermore, the terminal 810 cannot be removed from the housing 801, and thus the damaged terminal 810 cannot be replaced with a new terminal.